- Distortion caused by local static field variations in magnetic resonance imaging can be corrected by using a method developed by Chang and Fitzpatrick (CF) that requires two acquisitions identical except for the polarity of the read gradient. This approach has previously been applied to spin-echo imaging. In this report, its role in correcting geometric distortion in gradient-echo imaging is investigated using a dynamic programming algorithm. This approach appears to successfully handle many of the edge artifacts otherwise inherent in the CF method. Once the correction has been made, it is then possible to extract the local magnetic field itself. Magn Reson Med 42:585-590, 1999.